Low metalloid enameling steel and method of producing same



LOW METALLOID ENAIWELING STEEL AND lVIETHOD OF PRODUCING SAME Joseph C. Eckel, Pittsburgh, Pa., assignor to United States Steel Corporation, a corporation of New Jersey No Drawing. Application March 6, 1952, Serial No. 275,243

3 Claims. (Cl. 75-123) This invention relates to improvements in ferrous enameling stock of the type frequently referred to as low metalloid iron or steel.

Conventional low metalloid iron or steel used for vitreous enameling is subject to various defects which prevent the application of so-called direct or single white or light color coats thereto. The general defects are of three types, i. e., fish scales known as the delayed type, black specks, and a very fine dark colored misty elfect known as pull throng The first are sometimes attributed to the evolution of hydrogen gas at temperatures below about 1250 F. and the latter to the evolution of carbonaceous gases at temperatures exceeding 1250 F.

It is accordingly the object of this invention to provide enameling stock that can be given a direct white coat or light colored coat of enamel without delayed defects, black specks, or pull through.

It is a further object to provide an enameling stock that can be processed by a much more economical method than normalizing, or normalizing and box annealing, which is now the conventional practice, either in coils or cut lengths.

I have discovered that the foregoing and further objects can be attained by the conjoint addition of silicon and titanium to low metalloid iron or steel in certain minimum amounts. Such low metalloid iron or steel conventionally contains a total of carbon, manganese, phosphorus, sulphur and silicon of not more than 0.10% in one type, 0.15% and 0.20% in other types.

More specifically, I have discovered that to attain the benefits of the silicon and titanium additions, the silicon must be present in the sheet in amounts of at least 0.03% and the titanium should be present in an amount at least equal to at least five times the minimum silicon content, i. e., 0.15%. So far as the present invention is concerned, additions may vary Widely if the foregoing minimum amounts are present. However, for the sake of freedom from inclusions, slivers, etc., it is preferred to keep the silicon and titanium on the low side of the maximum, i. e., silicon below about 0.10%, preferably 0.05% to 0.07%, and titanium not over about 0.35%.

Direct white vitreous enameling tests conducted on samples of the following composition illustrate the beneficial effects of silicon and titanium additions within the foregoing ranges:

Enameling sheets of the foregoing composition were free of delayed defects such as fish scaling and black specks, when a direct coat of porcelain enamel was applied thereto.

Enameling defects were encountered, however, when- Patented Feb. 28, 1956 ever either the silicon or titanium was less than .03% or .15 respectively, as shown by the following Table II:

Table 11 Steel No 0 Mn Si Ti Thus, where steel Nos. 4 and 5 containing suflicient silicon but insufilcient titanium were direct white vitreous enameled, no delayed defects known as fish scaling occurred but black specks developed in the surface of the enamel coating; whereas steel No. 6 with sufiicient titanium but insufiicient silicon, delayed defects of the fish scaling type did occur. Samples of steel No. 7 which was low in both elements showed both types of defects.

I have further discovered that to attain the benefits of the invention and to obtain stock free from delayed defects and black specks, the titanium and silicon must be added simultaneously to the molten iron or steel while in the ladle or in the mold if desirable. This can be conveniently done by adding ferro-titanium having an adequate silicon content.

With this improved composition I have also discovered that the conjoint addition of silicon and titanium provides a stable oxide and stable carbide which eliminates the restricted or critical annealing temperatures which are essential in procuring enameling stock with unstable oxides and unstable carbides. Moreover, satisfactory enameling and mechanical properties are obtainable without resorting to the high cost of normalizing which must be followed by a costly pickling operation. Thus my improved composition permits the processing of low metalloid steel by any of the following methods:

By producing the hot band on a continuous hot strip mill, pickling, cold reducing the hot band to the desired thickness, box annealing at 1250 F. to 1550 F. and then temper passing if desired.

By producing the hot band on a continuous hot strip mill, pickling, cold reducing the hot band to the desired thickness, box annealing at 1550 F. to 1650 F. and then temper passing if desired.

By producing the hot band on the continuous hot strip mill, box annealing before or after pickling at 1550" F. to 1650 F., cold reducing to desired thickness, box annealing at 1250 F. to 1550 F. and then temper passing if desired.

While I have shown several specific embodiments of my invention, it will be understood that these embodiments are merely for the purpose of illustration and description and that various other forms may be devised within the scope of my invention, as defined in the appended claims.

I claim:

I. Low metalloid enameling stock containing less than .20% total metalloids and between .03% and .10% silicon and between .15 and .35 titanium with the balance substantially iron, said silicon and titanium combining to prevent fish scales, black specks and pull through upon application of a direct light-color vitreous enamel to said stock.

2. The method of eliminating the tendency of low metalloid enameling stock to cause black specks and fish scaling upon the application of a direct white vitreous enamel thereto comprising forming low metalloid steel having a total metalloid content less than .20% and then simultaneously adding sutficient silicon and titanium thereto while molten to produce at least .03% silicon and .15 titanium in the finished steel.

3'. As a; new article of manufacture, enameling stock containing less than 20% of carbon, manganese, phosphorus and sulphur and including between .03% and .10% silicon and between .15% and 35% titanium, the titanium content being at least 5 times the silicon content withthe balance substantiially iron, said silicon and titanium combining to prevent fish scales, black specks and pull through upon application of a direct light-color vitreous enamel to said stock.

References Cited in the file of this patent UNITED STATES PATENTS 1,5 5 5,234 Thuaud Sept. 29, 1925 FOREIGN PATENTS Great Britain Apr. 30, 1934 OTHER REFERENCES Titaniuin in Steel, pages 17, 44, 226, 234 and 23s. Edited by Comstock et 211., published in 1949 by the Pitman Publishing Co., New York. 

1. LOW METALLOID ENAMELING STOCK CONTAINING LESS THAN .20% TOTAL METALLOIDS AND BETWEEN 903% AND 910% SILICON AND BETWEEN, .15% AND 935% TITANIUM WITH THE BALANCE SUBSTANTIALLY IRON, SAID SILICON AND TITANIUM COMBINING TO PREVENT FISH SCALES, BLACK SPECKS AND PULL THROUGH UPON APPLICATION OF A DIRECT LIGHT-COLOR VITEROUS ENAMEL TO SAID STOCK. 